The invention relates to mobile communication systems and particularly to a method and apparatus for implementing call forwarding in a mobile communication system comprising at least one closed user group of at least one subscriber. The method comprises the steps of detecting conditional or unconditional call forwarding to a defined call forwarding number in connection with call set-up.
In addition to normal speech and data transmission, mobile communication systems provide a plurality of supplementary services for subscribers. Basic services according to the specifications have already been brought into use, and the number of more advanced services based on the intelligent network architecture increases continuously.
One supplementary service included in mobile communication systems is a closed user group. By means of the closed user group several different restrictions concerning the internal or external telecommunications can be defined for a selected group of subscribers. Call restrictions available include e.g. barring of incoming or outgoing calls and barring of long-distance or international calls. Closed user groups are typically applied in companies, in which it is desirable to restrict the use of mobile stations given to employees mainly to professional purposes. In the call set-up process, closed user groups cause additional checks, on the basis of which call set up is either continued normally or is discontinued due to call restrictions.
Another supplementary service provided by mobile communication systems is call forwarding which the subscriber can activate. Call forwarding can be unconditional, i.e. a call is always forwarded to a given new number. Call forwarding can also be defined as conditional e.g. when the subscriber is busy, does not answer, or is not reachable. The most commonly used forms of call forwarding are voice mail services (Voice Mail Service, VMS) in which the subscriber defines that his incoming calls are to be forwarded either unconditionally or conditionally to the VMS center. The center answers calls and stores the messages left for the subscriber.
Upon implementation of call forwarding to the voice mail in a closed user group, situations have arisen in which a call to a member of a closed user group succeeds normally, but call forwarding to the voice mail succeeds or fails depending on the call restrictions and definitions of outgoing access of the called party. For an ordinary user it is not easy to understand restrictions and definitions expressed as technical terms. Therefore, as regards the functionality and reliability of the system, it would be important to be able to utilize the voice mail without difficulty at least in those cases in which the actual call between two subscribers is possible.
An object of the invention is to provide a method and equipment implementing the method for solving the above-mentioned problem. The object of the invention are achieved with the method comprising the steps of checking whether call forwarding is directed to the voice mail, and performing call forwarding in response to the fact that call forwarding is directed to the voice mail, regardless of a possible bar to call forwarding due to interaction between the call forwarding facility and the closed user group.
The invention also relates to a subscriber data base in which the subscriber""s information on call forwarding is stored. The subscriber data base is characterized in that it is arranged to check whether call forwarding is directed to the voice mail, and to forward the call in response to the fact that call forwarding is directed to the voice mail, regardless of a possible bar to call forwarding due to interaction between the call forwarding facility and the closed user group.
The dependent claims relate to the preferred embodiments of the invention.
The invention is based on the idea that the system is arranged to check whether a defined call forwarding number is the number of the voice mail at least before call forwarding fails. If the system detects that the forwarding number in question is the number of the voice mail, checks related to call restrictions are omitted and the call is forwarded to the voice mail regardless of the possible call restrictions.
The inventive solution is implemented by storing the number or numbers of the voice mail in the subscriber data bases of the system and by arranging the subscriber data base to compare the call forwarding number with the voice mail number when forwarding is activated. If the numbers are identical, checks related to the call restrictions are not made.
The method and the system of the invention eliminate the possible problems caused by the restrictions of the closed subscriber group in connection with call forwarding to the voice mail.